TGSL Tuning & troubleshooting

[BKY1337]

I finally made it. I found two loose connections at the 8 Pin connector which was already soldered. There was an air gap between the feets and the PCB. I use a 9 V Battery now.
I dont think that the Testvoltage are alright but i could tune it and i could connect the Tx Coil.

I saw that the right TX hole at the pcb is number 1 not number 2. Because the PDF says i only get a Signal at J1-1. Its a nice Wave.

I got the following Voltages:

Vmax = -8,72
Vmin = -24,94
Vavv = -17,03
Vpp = 16,22
Vrms = 17,64

14,2 -14,7 kHz

The coil is not nulled , only two loose coils in an enclosure.

[ripsdevala]

Ok my turn... after put all in the box, i can't distinguish iron completely in disc mode, stilo detect a scissors at 5cm, i was change the connection of pot wire several time for wrong connection. Or maybe i left a piece solder tin inside and short something, any methods to find the problem before i change the ic and tr one by one?

[homefire]

I don't think you killed it ... Just follow through with the Trouble shooting as described on the Build Document.

[BKY1337]

I built the DSO today. Unfortunately i can not use it. My Power adapter was labeled with 9 Volts . But after a while i saw that it had 13,3V . I think some components got damaged.
The DSO boots up but the voltages are wrong , i dont have negative voltages at the tespoints and the backpack board doesnt produce a testsignal to tune it.
I also can not measure anything with it. Im slowly getting insane here.

Im sure if i should buy a new one for 26 Euro. And im not sure if it was the voltage which caused the problem. I guess the most ICs should endure voltages till 16 volt . The Manual said anything over 10V could destroy the ics. DAMN.

I had the 27cm with this old coil before the detector got damaged. Now i have only 20cm with this coil and only a weak signal. Too weak to use it.

[homefire]

Yep ! Those little DSO's are limited in abilities but you can do way more with that one channel then a DMM can ever do. Don't forget your input is limited to 50V Peak. My Hantek is limited to 5v but nothing a good probe can't fix.

[dbanner]

When your scope arrives, you'll be much happier man.

[bernte_one]

for myself i measure directly on rx coil
in past as i remind my target was to get under 10mV

if you measure after opamp the voltage will be much higher depending on the amplification factor

if i look Signal at your U103b it looks not bad

measure the null voltage mith a multimeter direct in Connection socket from plug on rx side, measuring area in mV (maybe 200mV Setting on your meter)

you can also fine tune your your coil after potting if you place a small Piece of metal foil on the coil
you can see how voltage and Signal drifts a Little

and if you can detect a coin at 27cm already, there can´t be much wrong

[BKY1337]

I have a Null Voltage of 4.00 V if i do this. I don't know why this coil had 27 cm with 1 euro.

[bernte_one]

if coil has wrong orientation of one side and it is already potted in epoxi and you have no chnce the flip one side then just try to Change the wire Connection on pcb
on one side, if you have luck the null voltage is still ok

[dbanner]

Then there is no way you get only milivolts on TX with your meter with detection distance of 20cm. Try measuring mains voltage and see what your meter reads.

[BKY1337]

My DMM can handle up to 200khz. My DSO150 will arrive tomorrow. I hope i can measure the voltage with it.

[dbanner]

The 11V-12V you measure before seems right as this would have been RMS value (.707 for sinusoidal) of peak to peak, which would translate to value of about 16-17 volts peak-to-peak. To convert RMS to peak to peak multiply by a factor of 1.414( for sinusoidal waves only.

[dbanner]

That 2.8 seems wrong. I'll have to do some math.

[dbanner]

I learned some DMM's measure average RMS(root mean square), good only for smooth sine wave, while others measure True RMS, good for all kinds, but again bandwidth of meter is important. I learned most cheap DMM's have bandwidth of between 50-500Hz. Not good enough to measure coil voltage. You need a meter that measures at least average RMS at a bandwidth of at least 20KHZ.For a cyclically alternating electric current, RMS is equal to the value of the D.C that would produce the same average power dissipation in a resistive load. In order to measure peak to peak voltage, you would have to multiply the RMS reading on meter by a factor of approx. 2.8(for true sine wave)

[dbanner]

Look at the schematic for clues, one side of Tx coil is grounded. This would be where shield connects. Now look for appropriate hole on pcb. AS for RX, the start/finish, well just flip the coil if you are getting the double beep thing, then this would correspond to start/ finish. If you didn't mark which wire was the start when you were winding coils, then it's not a problem.